<html><head>
 
<style>

select {
    width: 200px;
}
option {
    padding: 0;
    width: 50%;
    background-color: cyan;
}
</style></head><body>

<select size="3">
<option style="margin-right: 50%;">left</option>
<option style="margin-left: 50%;">right</option>
<option style="margin-left: 25%; margin-right: 25%;">center</option>
</select>

</body></html>
